JPH03108688A - Radiation detector sensitive to position - Google Patents

Abstract

PURPOSE:To facilitate manufacture of the title detector very much and to make a stray capacity between electrodes small by a method wherein at least one of parts divided in two electrically by a sawtooth-wave-shaped boundary part is divided at equal intervals in the direction intersecting perpendicularly the direction of extension of the boundary part. CONSTITUTION:Two divided areas are formed by a sawtooth-wave-shaped insulating slender wire 24, and moreover, each sawtooth is formed to be a small area 25 insulated from each other in one of the divided areas. Each small area is connected, one to one, electrically to each band-shaped area 16 of the surface of a charge divider 14, from the end sequentially, by a conductor 21, while the other area 26 is connected directly to a charge-sensitive preamplifier. A charge induced to a position detecting electrode 23 is divided in two in the direction Y first and further divided into many partial charges in the former area of the two. These partial charges are supplied through triangular electrodes 18 and 19 located at the back of the divider 14 and the position coordinates in the direction X are determined from the ratio of the quantities of electricity supplied from the electrodes 18 and 19. The position coordinates in the direction Y intersecting them perpendicularly can be determined from the ratio between the charges of the two areas divided by a sawtooth-shaped pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric radiation detector that detects the incident position of radiation such as α-rays, β-rays, X-rays, T-rays, etc.

(Prior art) An electric radiation detector is an electric charge generated inside the detector due to radiation, or an electric charge generated by multiplying this internally.
Alternatively, it refers to a radiation detector that extracts charges induced on electrodes by these as electrical signals. The radiation incident position is determined by arranging a plurality of independent detection elements (detection electrodes) and processing the output of each detection element.

The problem is that the arithmetic processing circuit used in this case becomes quite complex if high resolution is to be achieved. In contrast, a position-sensitive radiation detector has been proposed that detects the radiation incident position without requiring a complicated arithmetic circuit as a single detector.

As position-sensitive radiation detectors, resistance layer type and split electrode type are known. The resistive layer type utilizes the fact that charges generated at the incident position are divided by a resistance value that changes depending on the incident position.

Since this resistive layer type uses a resistive layer, the output pulse rises slowly, resulting in problems of low detection speed and low counting efficiency. A split-electrode position-sensitive radiation detector induces charges of opposite sign in a range on the signal readout electrode by charges generated by absorption of radiation, and the center position of this induced charge (electric center of gravity) is It is a type of detection using a charge-sensitive detector, and has the characteristics of high speed and high counting efficiency compared to the resistive layer type.

Here, as examples of split electrode type position-sensitive detectors, for example, pack-gammon type and wedge-and-strip type are known.

The backgammon type is as follows.

FIG. 5 is a conceptual diagram for explaining the principle. If a charge -Q is generated due to the incidence, a charge 51 having the opposite sign is induced on the electrode 50 placed below it due to electrostatic induction. The electrode 50 is divided into two regions 53 and 54 by a sawtooth thin wire insulating section 52,
The induced charge 51 is divided into regions 53 and 54 as QA SQB at a ratio proportional to the coordinate in the X direction in the figure. The X coordinate of the center of gravity of the induced charge is expressed as QA/(QA + QB).

Further, the wedge-and-strip type is as follows. FIG. 4 is a conceptual diagram for explaining the principle. The electrode 40 is divided into three regions, ie, a wedge region 43, an intermediate region 44, and a strip region 45, which are insulated from each other by a sawtooth-like thin wire insulating portion 41 and a rectangular wave-like thin wire insulating portion 42. The pitch of the sawtooth and square waves is constant and has an interdigitated structure. The band-shaped part between the sawtooth (wedge) of the square wave (
The width of the strip gradually decreases from left to right in the figure. The amount of charge induced in the wedge region 43, intermediate region 44, and strip region 45 is expressed as QA, Qa,
If Qc, the position of the center of gravity of the charge distribution in the X direction can be determined by QA/ (QA+Q!l+Qc), similar to the backgammon principle. On the other hand, regarding the position in the X direction, Qc
/ (QA+QB+QC).

(Problems to be Solved by the Invention) The above-mentioned split electrode type position-sensitive radiation detector does not degrade the signal rise time inherent to the measuring device at all, and there are no factors that extend the signal processing time for one radiation drawing. This makes it superior to the resistance method in high-speed, high-counting rate measurements.

However, the split electrode type has a shape with a segmented pattern, which makes it difficult to create when aiming for high resolution or when applying to a small area detector, and it has a pattern with an intricate structure. This results in an increase in stray capacitance, which poses a problem of limiting positional resolution.

(Means for Solving the Problem) The above-mentioned problem is solved by a plurality of strip-shaped electrodes having the same width arranged at regular intervals, and which are arranged opposite to these strip-shaped electrodes with an insulator interposed therebetween, and which overlap with the electrodes. This problem is solved by using a charge divider for reading the radiation incident position, which is composed of two triangular electrodes whose area increases and decreases linearly along the direction in which the strip areas are arranged.

(Function) By flowing charges based on incident radiation into the strip electrodes of the charge divider of the present invention, the incident position of the radiation can be easily determined by determining the ratio of the amount of charges generated in each triangular electrode. You can ask for it.

This charge divider can be made smaller by drawing the above pattern on a flexible double-sided substrate and folding it into a small size.

Further, the charge flowing into the strip electrode of the charge divider may be the charge induced in a plurality of strip electrodes, or may be a semiconductor,
The charge may be generated by an individual radiation detection element consisting of a bolometer. By arranging elements with excellent energy resolution and performing position detection in this manner, sophisticated position detection can be performed using extremely simple electronics.

Furthermore, the electrode of the charge divider can be connected to the anode of a microchannel plate, a parallel plate avalanche counter, or the cathode of a multiwire proportional counter.

(Effects of the Invention) In the charge divider of the present invention, since the electrodes are not divided into complicated shapes as in the divided electrode type, manufacturing is extremely easy and the stray capacitance between the electrodes is small.

By using a plurality of various high-sensitivity detection elements and connecting them to the strip electrode of the charge divider of the present invention, position detection can be performed by a simple arithmetic circuit.

The network of capacitance formed by the charge divider is
Since it is in series with the stray capacitance between the strip electrodes and is sufficiently larger than this, it does not contribute as a load capacitance to the charge-sensitive detector. Therefore, it does not increase electrical noise.

Since no resistor or delay line is used, it has advantages such as being able to construct a position-sensitive radiation detector with high speed and high counting rate.

(Example) Examples of the present invention will be described in detail below.

1A and 1B are a plan view and a side view of a one-dimensional radiation position detector using the charge splitter of the present invention. The incident position of the radiation is perpendicular to the position detection direction, and the insulator 12
This is achieved by detecting the position of the center of gravity of the charges induced in the position detection electrode 10, which is composed of a large number of mutually insulated parallel band-shaped electrodes 13 having a constant width. The position of the center of gravity of this charge is detected by the charge divider 14 of the present invention. This charge splitter 14 has a strip electrode 16 divided into a large number of parallel strip regions of a constant width which are mutually insulated by an insulator 15, and an insulator layer 1 with a thickness of -.
7 (FIG. 1B) is provided with two mutually insulated triangular electrodes 18 and 19 in the form of a rectangle divided by one diagonal.

Each strip electrode 13 on the position detection electrode 10 and the charge divider 14
The strip electrodes 16 are sequentially electrically connected one-to-one through conductors 22 from the ends. Each strip electrode 16 of the charge divider 14 has a time constant that is sufficiently long compared to the signal rise time specific to the measuring device in order to ultimately neutralize the charge due to ions, electrons, or holes collected on the position detection electrode. Connect to ground or the required high voltage terminal with a high resistance such that

In the charge divider 14, if the capacitance between the n-th strip electrode 16 and the triangular electrode 18 is ChA, and the capacitance between the triangular electrode 19 is C7, it increases linearly as Chaltn increases, C,,B decrease linearly as n increases. That is, if the amount of change is a, it will be expressed as CI,A=an+C, CIl,=-an+C. C
hA+CI,ll is constant regardless of n. Cl1A+
CIIB must be sufficiently large compared to the stray capacitance between each strip electrode, but in the charge divider of the present invention, the division between the electrodes is done by a simple straight line, so
The stray capacitance is smaller than that of the conventional one, and this condition is fully satisfied.

Charge q induced on the nth strip electrode 13. Then, Σq, =Q (total amount of induced charges).

Since the capacitance CnA+CIIB is sufficiently larger than the stray capacitance between the strip electrodes, qo is supplied from ClnA and C,,I+, and as a result, on the strip electrode side of Cf1A, Qh xchA/ (cnA+cr, n)Chll This means that a charge equal to Q h X CR11/(CWA÷C,a) is allocated to the strip-shaped electrode side, and the charge supplied from the triangular electrode 18 is Σ-q. xcnA/ (Cr, A
-! -Cr,a)=Q.

The charge supplied from the triangular electrode 19 is Σ-q. X C
rv/ (chA: Chll) = QB.

QA+Q, =Σ-q. =-Q Q^/ (Qa 1011) = b/d-”, a/
d In other words, location information is QA,
This means it was taken out by the QB.

Therefore, the target one-dimensional position can be determined by connecting the two triangular electrodes 18 and 19 on the back surface to charge-sensitive preamplifiers and performing calculations based on their two output values.

FIG. 2 is a plan view of a two-dimensional radiation position detector using the charge splitter of the present invention. The position detection electrode 18 shown here is roughly divided into two regions by serrated thin insulating wires 24, and in one region, each of the serrations is made into a small region 25 that is insulated from each other. Each of them is sequentially electrically connected to each band-shaped region 16 on the surface of the charge divider 14 in a one-to-one manner from one end to the other by a conductor 21 . The other region 26 is directly connected to a charge-sensitive preamplifier, and the two triangular electrodes 18, 19 on the back side of the charge divider 14 are each also connected to a charge-sensitive preamplifier.

The charge induced in the position detection electrode 23 is first divided into two in the X direction by the sawtooth pattern thereon, and at the same time, in one region, each sawtooth forms a small region insulated from each other. Therefore, it is further divided into many corresponding partial charges. These partial charges are supplied via the triangular electrodes 18.19 on the back side of the charge divider 14, and the ratio of the amount of electricity supplied from these triangular electrodes 18.19 is QA / (QA + QB) From, 1
The position coordinates of the sawtooth pattern in the repeating direction (X direction) are determined by the same principle as in the dimension case. Also,
The position coordinate in the X direction perpendicular to this is the ratio Qc / between both charges divided into two by the sawtooth pattern.
(QA+QB+Qc) can be determined using the same principle as the Backgasen method.

Another embodiment for two-dimensional position reading is shown in FIG. The conductor on the position detection electrode 30 is roughly divided into two regions in the X direction by a sawtooth insulated thin wire 31, and in both regions, each sawtooth is divided into triangular small regions 32, 32 insulated from each other. '. Each of them has a strip electrode 16.16' on the surface of the two charge dividers 14.14' on both sides.
The conductors 19 and 19' are sequentially electrically connected from the ends in a one-to-one manner. Each triangular electrode 18.1 on the back side of the charge divider
9.18' and 19' each connected to a total of four charge-sensitive preamplifiers. The charge induced in the position detection electrode 30 is
The sawtooth pattern on it divides it into two large areas in the
It is further divided by direction. These partial charges are transferred to a total of four triangular electrodes 15.16.15'16 on the back side of the charge divider.
′ will be supplied via the capacity network.

The position coordinate of the sawtooth pattern in the repeating direction (X direction) is determined by the ratio of the sum of charges extracted from the triangular electrodes 18 and 18' of the two charge dividers to the total amount of induced charge, that is, (QA
+QC) / (QA +QB +Qc-i-Qo). In addition, the position coordinate in the X direction perpendicular to this is the ratio between both charges divided into two by the sawtooth pattern (Q c ÷ Qo) / (QA + QB
+Qc +Qo) can be determined using the same principle as the packgammon type.

In the method shown in Fig. 2, when the detected charge approaches the right end of the detection electrode, QA + QB becomes small and the position resolution in the X direction may deteriorate, but with the method shown in Fig. 3, This problem does not occur because the denominator is the total induced charge in both directions.

[Brief explanation of drawings]

1A and 1B are a plan view and a sectional view, respectively, of a one-dimensional radiation position detector using the charge divider of the present invention, and FIG. 2 is a two-dimensional radiation position detector using the charge divider of the present invention. FIG. 3 is a plan view of another two-dimensional radiation position detector using the charge splitter of the present invention; FIG. 4 is an explanatory diagram of a pack-gammon type position-sensitive radiation detector; The figure is an explanatory diagram of a wedge-and-strip type position-sensitive radiation detector. (Explanation of symbols) Q... Generated charge, 51... Induced charge region, 51, 41.42.15.24.31, curved/thin wire-shaped insulating part, 10... ...One-dimensional position detection electrode, 14.
14'...Charge divider, 16.16'...
...Strip conductor of charge divider, 17...Insulator layer, 18.19...Triangular electrode, 21.21'...Conductor, 23.30... ...Two-dimensional position detection electrode, 25.3
2.32'...Small area conductor. Figure 2: Engraving of drawings (no change in content) Figure 1A Figure 18.19 Figure 4 QB Procedural amendment (method) 1. Indication of the case 1999 Patent Application No. 247609 2. Title of the invention Position is sensitive Radiation detector 3, Person making the amendment Name of applicant related to the case (679) RIKEN 4, Agent 5, Date of amendment order December 26, 1999 6, Drawing subject to amendment 7, Contents of amendment Procedural amendment 2. Bo19 Heisei year month date

Claims (2)

[Claims] (1) Multiple strip electrodes of equal width arranged at regular intervals,
and a radiation beam consisting of two triangular electrodes arranged opposite to these strip electrodes via an insulator, and whose overlapping area with each electrode increases and decreases linearly along the arrangement direction of the strip electrodes. Charge divider for reading the incident position. (2) In combination with the charge divider according to claim (1), which is divided into two parts by a sawtooth wave, and at least one part is further divided at equal intervals in a direction perpendicular to the direction in which the sawtooth wave extends. Electrode used to detect the position of radiation incidence.